Usability is a property of devices (interfaces, work methods, software, and so on) but it's also a field-and some would say it's a profession. Here, we examine the concept of usability from the standpoint of human-centered computing. Manifestly, the two should be quite closely related. The principles of HCC that have been explored in this department dictate a prime goal for intelligent technology: It must be useful, understandable ... and usable.